Breech mechanism for automatic or semi-automatic guns

ABSTRACT

The breechblock slides in a casing which in turn slides nonrotatably in the breechcase. Mechanical means transform into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, when the breechblock has substantially reached its front closing position, for locking the breechblock by co-operation between the barrel and locking lugs formed on the breechblock. At least a portion of each one of (a) the external surface of the locking lugs, (b) the external surface of the casing and (c) the internal surface of the breechcase, lies on a common geometrical cylinder of revolution such that the breechblock is guided along the internal surface of the breechcase by the engagement both of the external surface of the lugs and of the external surface of the casing on the internal surface of the breechcase.

Unite States Patent Maillard 1 Sept. 12, 1972 [22] Filed:

[72] Inventor: Bernard Maillard, l4, Chateau Banquet, Geneva, Switzerland Jan. 6, 1970 [21] App1.No.: 928

Related US. Application Data [62] Division of Ser. No. 717,524, April 1, 1968,

Pat. No. 3,447,418.

[52] US. Cl ..89/l85 [51] Int. Cl ..F4ld 3/06 [58] Field of Search .'..42/16 R, 16 A, 17 A, 18 A,

42/19 A, 20 A, 25, 25 A; 89/171, 172, 184,

8/1954 Crittendon et al ..89/185 X 3/1971 Stoner ..89/l72 Primary Examiner-Stephen C. Bentley Attorney-Larson, Taylor & Hinds ABSTRACT The breechblock slides in a casing which in turn slides non-rotatably in the breechcase. Mechanical means transform into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, when the breechblock has substantially reached its front closing position, for locking the breechblock by co-operation between the barrel and locking lugs formed on the breechblock. At least a portion of each one of (a) the external surface of the locking lugs, (b) the external surface of the casing and (c) the internal surface of the breechcase, lies on a common geometrical cylinder of revolution such that the breechblock is guided along the internal surface of the breechcase by the engagement both of the external surfaceofthe lugs and of the external surface of the casing on the internal surface of the breechcase.

7 Claims, 8 Drawing Figures BREECH MECHANISM FOR AUTOMATIC OR SEMI-AUTOMATIC GUNS REFERENCE TO RELATED APPLICATIONS This application discloses and claims subject matter disclosed and claimedin my earlier applications, Ser. Nos. 717,621, filed Apr. 1, 1968 and issued as U.S. Pat. No. 3,507,187 on Apr. 21, 1970 and U.S. application Ser. No. 810,863, filed Oct. 2, 1968 and issued as U.S. Pat. No. 3,561,148 on Feb. 9, 1971, this latter application being a division of my earlier application, Ser. No. 7 17,524, filed Apr. 1, 1968 and issued as U.S. Pat. No. 3,447,418 on June 3, 1969.

The present invention relates to breech mechanisms for automatic and semi-automatic guns of the type including a breechblock adapted to be locked by rotation and which is provided, on the one hand, at the front part thereof, with a cup-shaped recess in which is engaged the rear part of a cartridge to-be fired, and, on the other hand, on the outside, with locking lugs which co-operate with lugs provided in a sleeve rigid with the gun barrel, the breech mechanism further comprising a casing surrounding the breechblock and slidable longitudinally without rotation in a breechcase, means being provided between said casing and the breechblock to transform into a rotary movement of the breechblock (which is then locked) at least a portion of the translatory motion that takes place between the casing and said breechblock once the latter reaches substantially its front closing position, The object of the present invention is to provide a breech mechanism which is better adapted to meet the requirements of practice than those known at the present time.

According to a first feature of the present invention, in a breech mechanism of the type indicated above, there are provided on a common geometrical cylinder of revolution, on the one hand, the external surface of the breechblock lugs and at least a portion of the external surface of the .casing surrounding the breechblock, and on the other hand, at least a portion of the internal surface of the breechcase, whereby the breechblock is guided along this portion of the internal surface of the breechcase not only by the casing but also by at least some of the breechblock lugs. For the sake of convenience, said portion of the internal surface of the breechcase will be called hereafter cylindrical portion, it being understood that this portion does not necessarily form an entire cylinder, but may form only part or parts of a cylinder.

A second feature of the present invention consists, in a breech mechanism of the type indicated above, in providing, in the lateral outer surface of the casing, two diametrically opposed longitudinal bosses, the lateral longitudinal faces of which co-operate with guiding faces provided in the breechcase for the purpose of preventing the casing from rotating inside the breechcase, one of these bosses having a front face adapted to co-operate with a sear for stopping the breech mechanism whereas the other of these bosses has a front face adapted to co-operate with the device for unlocking the breech mechanism from the breechcase, on the one hand, and with the resetting device, on the other hand, which last mentioned boss may possibly co-operate through the rear portion thereof with an ejector for rocking this ejector.

A third feature of the present invention consists, in a breech mechanism of the type indicated above, in separating the lugs of the breechblock from one another by angular spaces one of which accommodates an extractor carried by the breechblock whereas the angular space diametrically opposed to the preceding one extends as far as the inside of the cup-shaped recess to provide a passage for an ejector carried by the breechcase.

A fourth feature of the present invention consists, in a breech mechanism of the type indicated above, in providing, on the one hand, directly between the breechblock and the casing, a blocking device adapted to work at the end of the unlocking of the breech mechanism, for imperatively maintaining said casing in the extreme rear position with respect to the breechblock during the reciprocating movement of the breech mechanism inside the breechcase and, on the other hand, on the breechcase, a release device adapted to act, at the end of the breech mechanism closing operation, upon the blocking device for making it inoperative.

A fifth feature of the present invention consists, in a breech mechanism of the type indicated above, in distributing the breechblock lugs along at least two annular rows the rear active faces of which are located on two identical but distinct skew helical lines spaced axially at a distance from each other greater than the pitch of said helical lines.

The present invention further relates to breech mechanisms for automatic or semi-automatic guns of the type which comprise, on the one hand, a breechblock provided, at the front end thereof, with a cup-shaped recess into which is engaged the rear part of a cartridge to be fired, said breechblock being adapted to be locked with respect to an element rigid with the gun barrel, and, on the other hand, a locking member for controlling (control stroke) and maintaining (safety stroke) the locking of the breechblock, this member being mechanically connected with a firing pin movable with respect to the breechblock and subjected to the action of at least one firing spring bearing upon the breechblock. This invention is more especially, but not exclusively, concerned with breech mechanisms of the type first indicated above, wherein this locking member is essentially constituted by said casing and is adapted to rotate the breechblock in one direction (control stroke) so that the lugs it carries are screwed in front of the lugs carried by the breechcase, then to perform a safety stroke preventing the breechblock from rotating in the opposed direction.

A sixth feature of the present invention consists, in a breech mechanism of this second type (and possibly also of the first type indicated above), in using a semipositive connection between the firing pin and the locking member (casing) such that, when the locking member has only partly completed the safety stroke, the firing pin can reach the primer of the cartridge received in the cup-shaped recess to fire it before the end of the safety stroke.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings given merely by way of example, and in which:

FIG. 1 is a longitudinal sectional view of a breech mechanism made according to the present invention and of the gun elements that co-operate with this breech mechanism;

FIG. 2 is a view similar to FIG. 1 showing a breech mechanism made according to a first modification;

FIG. 3 is a transverse sectional view, in particular on the line IIIIII of FIG. 2, of one of the breech mechanisms of FIGS. 1 and 2;

FIG. 4 is a separate view of the breechblock in longitudinal section analogous to that of FIGS. 1 and 2;

FIG. 5 shows, from the left hand side of FIG. 4, the same breechblock with, in cross section, the ejector;

FIG. 6 is a view of the breechblock of FIG. 4 seen from above;

FIG. 7 is a longitudinal half-section showing some of the elements of FIG. 1 in a different working position; and

FIG. 8- shows, similarly to FIG. 3, a breech mechanism made according to a second modification.

The particular embodiments illustrated by way of example in the drawings relate to automatic guns of calibre comprised between 20 and 40 mm.

The breech mechanism comprises a breechblock 1 which is locked by rotation, this breechblock including, on the one hand, at the front thereof, a cup-shaped recess 2 which engages the rear part of the cartridges to be fired (not shown) and, on the other hand, at the periphery thereof, locking lugs 3 adapted to co-operate with corresponding lugs 4 provided in a sleeve 5 rigid with gun barrel 6. The breech mechanism further includes a casing 7 surrounding breechblock l and slidable longitudinally without rotation in breechcase 8. Means are provided between the casing 7 and the breechblock 1 for transforming into a rotary movement of the breechblock 1 (and to lock said breechblock by the intermediary of lugs 3 and 4) at least part of the translatory motion which takes place between the casing 7 and said breechblock 1 when said breechblock arrives substantially in its front closing position (position shown in FIGS. 1 and 2).

Breechblock l is made of a single piece (see, in particular, FIGS. 4 to 6) of substantially cylindrical shape about axis X-X which coincides both with the axis of rotation of this breechblock and with the axis of barrel 6. Said breechblock 1 projects from casing 7, at the rear thereof, through a hole 9, whereby the rear face 10 (FIG. 1) or 10a (FIG. 2) of said breechblock 1 cooperates with the conventional breech mechanism damping device 11 carried by the rear portion of breechcase 8.

In the embodiment of FIG. 2, the rear face 10a of breechlock 1 co-operates directly with said damping device 11 (similar to that diagrammatically shown by FIG. 1). According to the embodiment of FIG. 1, the rear face 10 of the breechlock l constitutes a bearing face for a plug 12 mounted on said breechlock by means of a bayonet joint 13, the rear of this plug being interposed between said face 10 and damping device 1 1.

Whatever be the embodiment that is chosen, breechblock 1 extends from the rear to the front of the breech mechanism and determines substantially (that is to say except for the thickness of plug 12) the length of the breech mechanism, which is thus greatly reduced.

To facilitate assembly, casing 7 is advantageously made of two casing elements or shells 7a and 7b adjoining each other along a diametral plane (plane of FIGS. 1, 2 and 7) and ridgidly interconnected in the longitudinal direction by radial studs 14 (for instance one stud carried by easing element 7a located between two studs carried by casing element 7b, as shown by FIGS. 1,2, 3 and 7).

A transverse spindle 15 extends across breechlock 1 in a manner that will be hereinafter explained. This spindle is connected, inside breechlock 1, with a firing pin 16 (FIGS. 1 and 7) or 16a (FIG. 2) to operate it; and spindle 15 is connected, outside this breechlock 1, without play, to casing 7. Breechlock l is provided with a longitudinal recess 17 which, in the absence of a plug such as 12, is open towards the rear and receives the body of firing pin 16 and guides it with a translatory movement parallel to axis X-X. Furthermore, to accommodate firing pin 16 or 16a, breechlock 1 is provided, at the front thereof, with a passage 17a which opens into cup-shaped recess 2.

According to the embodiments of FIGS. 1, 2, 3 and 7, spindle 15 has one end thereof engaged in the element 7a of easing 7 and the other end thereof in element 7b. According to the modification of FIG. 8, wherein the elements are designated by the same reference numbers as in the other figures, but increased by 100, spindle 115, connected to firing pin 116, is located in the plane of assembly of elements 107a and l07b and is therefore engaged, at each end thereof, half in element 107a and half in element 107b.

According to a first feature of the invention, the outer surface of the lugs 3 of breechblock l is located in the same geometrical cylinder of revolution C (FIGS. 1, 2 and 5) as at least a portion of the outer surface of easing 7. The diameter D of this cylinder is equal to the inner diameter of a cylindrical portion 18 of breechcase 8, along which cylindrical portion 18 move lugs 3 and easing 7. It is pointed out that lugs 3, as visible in FIGS. 1 and 2, are not located in the plane of these figures (see FIG. 5), which explains why their lower outline does not coincide with the intersection of cylinder C and said plane.

Thus, during its reciprocating movement, breechblock l is guided along cylindrical portion 18 not only by contact with casing 7 (in the manner which will be hereinafter described) which is itself in contact with said portion 18, but also by direct contact of at least some of its lugs 3 with this portion 18.

In order to transform the translatory movement of breechblock l with respect to casing 7 into a rotary movement of said breechblock about the axis of the gun barrel when the breechblock reaches substantially its front closing position, illustrated by FIGS. 1 and 2, spindle 15 carries two cylindrical rollers 19 (FIG. 3) adapted to co-operate with partly helical surfaces 20 (see also FIG. 4) provided in a cylindrical enlarged portion 21 of breechblock l, at least one of the end faces 21a and 21b of this cylindrical enlarged portion 21 limiting the longitudinal movements between casing 7 and breechblock 1. As shown by FIG. 4, each of said surfaces 20 comprises a helical rear portion of a length equal to a, which corresponds to the locking stroke of casing 7, and a rectilinear front portion parallel to axis XX, of a length equal to b, which corresponds to the safety stroke of casing 7.

Cylindrical enlarged portion 21 has an external diameter equal to the inner diameter of the recess 22 provided in casing 7 to accommodate said portion 21. On either side of cylindrical enlarged portion 21, breechblock 1 includes two cylindrical surfaces 23 and 24 on which elements 7a and 7b fit in a relatively fluidtight manner so as to form between them said recess 22 the length of which is sufficient to permit displacement of easing 7 with respect to cylindrical portion 21, elements 7a and 7b fitting together in a relatively fluidtight manner along their diametral plane of separation (plane of FIGS. 1 and 2).

For this purpose, elements 7a and 7b are provided with two inward annular projections 25 and 26 which limit recess 22 between them and the inner diameters of which are equal (with the approximation corresponding to clearance) respectively to the diameters of cylindrical surfaces 23 and 24 against which these projections are applied. Rear projection 26 has a front face 26a (forming the rear wall of recess 22) which, as shown'by FIGS. 1 and 2, constitutes an abutment for the rear end face 21b of enlarged portion 21'. Front projection 25 has a rear face 25a (forming the front wall of recess 22) which, as shown by FIG. 7, constitutes an abutment for the front end face 21a of enlarged portion 21. The movement of easing 7 toward the front may further be limited by contact of the front face 25b of the projection 25 of said casing 7 with a shoulder 27 provided on breechblock 1 (FIGS. 1 and 2). Likewise, the movement of casing 7 toward the rear may further be limited by contact of the rear face 26b of projection 26 either with the front face of plug 12 (FIG. 7) or with projections 39 (FIG. 2) provided at the rear end of breechblock 1. It should be noted that radial studs 14 are provided at the level of rear projection 26.

Thus, recess 22 is made practically fluidtight, the openings defined by surfaces being closed by casing 7 whatever be the relative axial position thereof with respect to breechblock 1. Owing to this fluidtightness, there is obtained a protection of the locking and unlocking mechanisms of the breechblock against the penetration of dust, sand, powder combustion residues and the like.

According to the modification of FIG. 8, the means for giving breechblock 1 its rotary locking movement consist of two aligned radial trunnions 28 carried by breechblock 101. Said trunnions 28 carry respective cylindrical rollers 119 engages in partly helical surfaces 120 provided in casing 107. As shown by this FIG. 8, trunnions 28 extend along a line at right angles to spindle 115. Reference character A indicates the amplitude of the angular displacement of breechblock 101 which produces its looking or its unlocking. Like surfaces 20 (FIG. 4), surfaces 120 include, in addition to a helical portion, a rectilinear safety portion.

According to-a second feature, the lateral outer surface of easing 7 forms two diametrically opposed longitudinal projections 29 and 30, the longitudinal faces 29a and 30a of case 8, so as to prevent casing 7 from turning inside said breechcase. Projection 29 is provided with a front face 29b adapted to co-operate with a sear 32 (FIG. 1) to stop the breech mechanism in the open position whereas projection 30 is provided with a front face 30b adapted to co-operate with a device 33 (such as a push-piece actuated by a gas-tap in the gun barrel) provided for releasing the breechblock with respect to breechcase 8 (FIG. 1), on the one hand, and with resetting device 34 (FIG. 2) which permits of resetting breechblock 1 before the beginning of the firing, on the other hand. Projection may still, according for instance to the embodiment of FIG. 2, cooperate at the rear with an ejector 35 (FIG. 5) for rocking it. A suitable ejector of this type is shown in greater detail in my copending application, Ser. No. 810,863, filed Oct. 2, 1968, now U.S. Pat. No. 3,561,148 issued on Feb. 9, 1971, which is a division of my previous application Ser. No. 717,524, filed Apr. 1, 1968, now U.S. Pat. No. 3,447,418, issued June 3, 1969. On the contrary, according to the embodiment of FIG. 1, it is the lower portion 38a of plug 12 that is arranged to rock ejector 35. Anyway, projection 30 is provided with a longitudinal 30c for the passage of a part of the ejector.

Preferably advantage is taken of the increased thickness corresponding to projections 29 and 30 to provide therein the radial studs 14, which, as stated, above, extend inwardly as far as projection 26.

Concerning plug 12 (FIG. 1), it advantageously comprises guiding means which co-operate with breechcase 8 both to hold the plug radially and to prevent it from rotating, this plug forming a support on the one hand,

. toward the rear, for a counter-recoil spring 36, and on the other hand, toward the front, for a firing pin spring 37 housed in the recess 17 of the plug 12 at the rear of firing pin 16. Counter-recoil spring 36 bears, at the front, either against breechblock 1 (FIG. 1), or against casing 7 (FIG. 2). The guiding means in question may consist of projections 38 which are integral with plug 12 and which have a profile analogous to that of casing 7 with its projections 29 and 30, which enables it to cooperate on the one hand with cylindrical portion 18 (FIG. 3) for radial guiding and on the other hand with guiding faces 31 for maintaining a fixed angular position. The lower portion 38a of plug 12, which actuates the ejector, is then carried by the lower projection 38. Of course, bayonet joint 12 must be adapted to enable breechblock 1 to rotate with respect to plug 12 when said breechblock is locked or unlocked by rotation.

The breechblock is thus guided not only, as explained above, by at least some of its lugs 3 and casing 7, but also by plug 12. Due to the fact that said plug has a fixed angular position, counter-recoil spring 36 does not interfere with its operation.

In the embodiment of FIG. 2, plug 12 is replaced by a plug which is nearly wholly housed in the recess 17 of breechblock 1, without the possibility of being acted upon by counter-recoil spring 36, which can then bear against breechblock 1, or preferably, as shown, against the rear of casing 7. Plug 12a, which acts as rear support for firing pin spring 37, is provided with a longitudinal slot 40 so that it is possible to deform it resiliently by urging toward each other the projections 41 provided at the rear thereof, for introduction into recess 17. Then said projections 41 are allowed to move away from each other so as to engage into notches provided on the inside of breechblock 1 (as shown by FIG. 2).

According to a third feature, the lugs 3 of the breechblock 1 are separated from one another by an gular spaces c, d one of which accommodates an extractor 42 (FIGS. 1 and 2) carried by breechblock 1 whereas the angular space diametrically opposed to the preceding one extends as far as the inside of the cup-shaped recess 2 to provide a passage 43 (FIGS. 1, 2 and 4) for ejector 35 which is carried by the breechcase 8. In the embodiment shown by the drawings, an angular space of 360/(2n+l) is provided between the lugs 3 of the breechblock l, where 2n is the number of lugs 3 (n being an integer). All the lugs 3 have the same peripheral development, so that, between two particular adjacent lugs 3 there is left an angular space (FIG. 5) greater than the angular space d extending between the other adjacent lugs taken two by two. This large angular space 0 accommodates extractor 42, whereas the small angular space d that is located opposite to said large angular space c forms part of passage 43.

Extractor 42 is housed in a slot 44 (FIG. 4) provided between two lugs 3 and it is kept toward the front and radially toward the outside by a heel 42a carried by said extractor and engaged in a recess 45 of breechblock 1 so as to form a bearing and pivoting abutment as shown in FIGS. 1 and 2. This extractor is kept in position longitudinally toward the rear by a leaf-spring 46 which tends to make it penetrate into cup-shaped recess 2. Leaf-spring 46 is fitted at the rear into the cylindrical enlarged portion 21 of breechblock 1, said spring 46 being itself held longitudinally by an expansible ring 47. Breechblock I is provided with a passage 48 (FIGS. 4 and 6) whose width is equal to that of spring 46. Passage 48 extends rearwardly from recess 45 to the inside of enlarged portion 21, overhanging edges 49 being provided in said enlarged portion to hold spring 46 therein. Passage 48 is provided at the fear thereof with a cylindrical housing 50 whose axis is radial, and which is adapted to accommodate expansible ring 47. The latter is of a height such that it is kept in position by casing 7 as shown by FIGS. 1,2 and 3.

According to the embodiment illustrated (see in particular FIG. 5 n is equal to 3 so that breechblock l is provided with six lugs 3 spaced apart by 360/7, with the exception of the two upper lugs which are at 72()/7 from each other. These angular spacings are measured from the middle 'axis of one lug to the middle axis of the next lug, and thus do not take into account the circumferential width of the lugs.

According to a modification (not illustrated), an angular space of l80/( n+1) is provided between the lugs of the breechblock distributed in two symmetrical groups, where 2n is again the number of lugs which have substantially the same peripheral development. There are two diametrically opposed large angular spaces of 360/( n+1) one of which accommodates extractor 42 whereas the other provides passage 43.

According to a fourth feature there is provided, on the one hand, directly between breechlock l and casing 7, a blocking device adapted to come into play at the end of the unlocking of the breech mechanism, to hold casing 7 imperatively in its extreme rear position with respect to breechlock 1 (position illustrated by FIG. 7), during the reciprocating movement of the breech mechanism in breechcase 8 and, on the other hand, on said breechcase, a release device located to act, at the end of the breech mechanism closing movement, upon the blocking device to put it out of action.

Preferably, said blocking device comprises a strip 51 (FIGS. 1 and 7) carried by breechblock l and the rear end of this strip is resiliently urged (preferable by the elasticity of the strip itself) radially away from the external surface of breechblock, that is to say into the path of the front face 26a of projection 26. The release device includes a piece provided with an inclined face 52 carried by breechcase 8, a push-piece 53 housed in casing 7 being interposed between said inclined face 52 and strip 51. Advantageously (as shown), said strip 51 has its front end tightly held in the rear part of enlarged portion 21, which is provided for this purpose with a passage 52 (FIG. 4) limited at the front by projections 54a serving to wedge strip 51.

It should be noted that, in order to simplify the drawings, it has been supposed in FIGS. 1, 2 and 3 that extractor 42, passage 43, spring 46 and strip 51 are located in the plane of assembly of shells 7a and 7b. In reality, this condition is complied with only when (contrary to the case of FIGS. 1, 2 and 3) casing 7 is located in its extreme rear position with respect to breechblock l, as shown by FIG. 7 where strip 51 is shown correctly in said plane of assembly, due to the rotation of breechblock 1 with respect to casing 7 as permitted by the recoil movement of the latter.

According to a fifth feature, the lugs 3 of the breechblock l are distributed in two annular rows the active rear faces f of which are located along two skew helical surfaces H and H (FIG. 6) identical to each other but distinct, and which are spaced apart in the axial direction by a distance I from each other greater then the common pitch p of said helical surfaces. Reference characters 30 and 3b designate respectively the two rows of lugs 3. The advantage of this construction consists in the lengthening of at least some of said lugs 3 in the axial direction. This is due to the fact that, if the faces f of all the lugs 3 were located in the same helical surface, as usual, their axial length could be at most equal to the differences between the pitch p and the axial length of the lugs 4 of sleeve 5 which must pass between the lugs 3a and 3b of the two successive rows.

Furthermore, each beginning 56 and each end 57 of the rows of lugs 3a and 3b advantageously line the large angular space c (FIG. 5) provided for extractor 42 (FIGS. 1 and 2), which facilitates the machining of lugs 3 which would tend to be rather delicate in view of the offsetting of helical surfaces H, and H According to a first solution, the helical surfaces H and H and also the helical surface H in which are located the front faces q of the rear lugs 3b, have inclinations such that reversibility of the movement is prevented. The term inclination" designates the angle between two planes passing through any perpendicular to the axis X-X of the helical surfaces, namely a plane tangent to this helical surface and a plane perpendicular to said axis. Reversibility means that a thrust exerted from left to right on breechblock 1, from the position shown by FIGS. 1 and 2, is capable of rotating said breechblock despite friction phenomenons. In order to prevent reversibility the angle in question may be given a value of about 5 or less.

According to a second solution, helical surfaces H,, H and H have inclinations such that reversibility of the movement is permitted, the angle defined above being then generally at least equal to 6 or 7.

The lugs 3 of the breechblock 1 may also be distributed in at least one row whose rear face f would be breechblock.

According to the preceding .description, the gun comprises locking means (casing 7) for controlling (control stroke a, FIG. 4) and maintaining (safety stroke b) the locking of breechblock l with respect to an element (sleeve 5) rigid with the gun barrel 6, this means being mechanically connected with firing pin 16a movable with respect to breechblock l and subjected to the action of at least one firing pin spring 37 bearing upon the breechblock.

According to a sixth feature, which is preferably applied to the locking means described above but which may be applied to locking means of a different type (for instance adapted to'operate locking members carried by a non-rotary breechblock), a semi-positive connection is used between the firing pin 16a and the locking means, such that, while the locking means (casing 7) have moved only aportion of the safety stroke, firing pin 16a can reach the primer of the cartridge (that is to say project into cup-shaped recess 2) and fire it before the end of said safety stroke.

According to the embodiment of FIG. 2 it suffices for this purpose to provide firing pin 16a with a slot 55 elongated in the direction of the axis X-X, extending. through firing pin 16a. Preferably, firing pin 16a is given a weight such that it opposes rebounding of the locking means or casing 7. This feature will be better understood by comparing the structure of FIG. 2 with that of FIG. 1 where spindle extends through firing pin 16 through a hole leaving no longitudinal play and where the firing pin is of smaller volume and therefore less heavy.

Owing to the anticipated firing thus achieved, a

higher rate of firing and an improved safety of operation are obtained.

The breech mechanism described ,above works as follows: Beforefiring, casing 7 is held in a rear position by sear 32 (FIG. 1) which co-operates with its face 29b. Breechblock l is also held in a rear position. Casing 7 is further held in its rear position with respect to breechblock l (as shown by FIG. 7) by the fact that strip 51, fixed to said breechblock, bears upon the face 26a of the casing. Firing pin 16 or 16a is also kept in its rear position, against the action of spring 37, with respect to breechblock 1 by spindle l5 rigid with casing 7.

By acting upon sear 32, the gunner releases the whole of the breech mechanism with casing 7. The whole breech mechanism is thrust in the frontward direction by counter-recoil spring 36 and receives in cup-shaped recess 2 a cartridge which is introduced into barrel 6. Once push-piece 53 comes to the level of inclined face 52, strip 51 is retracted into the position of FIGS. 1 and 2 and releases casing 7 with respect to breechblock 1. When said breechblock has reached approximately its closing position, shown by FIGS. 1 and 2, its lugs 3 come ahead of the lugs 4 of sleeve 5, which permits rotation of the breechblock. Firing pin spring 37, acting through firing pin 16 or 16a and spindle l5, drives toward the frontcasing 7 which is guided in such manner that it can have no movement of rotation about itself. It follows that spindle 15, which carries rollers 19, first assumes a movement corresponding to the helical portion a of inclined surface 20 (FIG. 4), thus rotating breechblock l and screwing the lugs 3 thereof in front of the lugs 4 of sleeve 5. Then spindle 1.5, moving along the rectilinear portion b (safety stroke) of surface 20, prevents a reversing of the rotation which would release the breechblock. At the same time, firing pin 16 or 16a is driven frontwardly and enters recess 2, thus firing the primer of the cartridge present in the barrel.

According to the embodiment of FIG. 2 the longitudinal play permitted by slot 55 enables firing pin 16a to strike the primer before the end of the safety stroke b (advanced firing), then to come into contact with breechblock l which limits the forward movement of said firing pin. As the time of firing of the cartridge is of the order of 2/ 1,000 of a second, casing 7 and spindle 15 keep moving forward up to the position (end of stroke) shown by FIG. 2 and, in case said casing and spindle l5 rebound (for instance when the time of firing exceeds 2/ 1,000 of a second), they meet during their rearward movement, resulting from rebounding, the rear end of the slot 55 of firing pin 16a which, due to its weight, will stop their movement.

After the cartridge has been fired, the gases developed in barrel 6 (or any other equivalent device) cause push-piece 33 to move rearwardly, breechblock 1 remaining stopped by its lugs 3. Spindle 15, which carries rollers 19, after having moved through safety stroke b, reaches helical path a and causes breechblock l to rotate in the unlocking direction. At the end of the unlocking stroke, the elements come back into their relative mutual positions of FIG. 7 where they are maintainedby strip 51. According as the gunner continues or not to act on sear 32, the breech mechanism is either driven again in the frontward direction or retained by said sear.

In view of the inclination of the faces f and g of the lugs 3 of breechblock 1 and of the corresponding faces of the lugs 4 of sleeve 5 (with or without reversibility), a longitudinal relative movement takes place during the locking and unlocking strokes.

This leads to the following advantages.

On the one hand, during locking, breechblock 1 can be in rotation (due to the relative longitudinal displacement of the casing caused by the firing pin spring and the counter-recoil spring 36) before it comes into abutment at the end of the frontward stroke (about l.5 mm), and on the other hand, during unlocking, breechblock l, which drives the extractor in its relative rearward movement, permits of detaching the cartridge case to be extracted from the cartridge chamber when the residual pressure in the gun barrel is still relatively high and before the casing reaches the end of its unlocking stroke toward the rear.

In the case of reversibility,- there is further obtained a self unlocking of the breech mechanism, after the controlled recoil of easing 7 in the safety stroke b (FIG. 4) owing to the thrust transmitted by the case of the cartridge that has just been fired, which could, for example, permit the rate of fire to be increased.

While the above description discloses preferred embodiments of the invention, it should be understood that said invention is not limited thereto, as there might be changes made in the arrangement, disposition and form of the parts without departing from the spirit or scope of the invention.

Iclaim:

1. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase about the breechblock for longitudinal sliding movement, and means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place when the breechblock has substantially reached its front closing position at which it closes off the rear end of the barrel, the improvement wherein: the said means at the forward end of the breechblock comprises a cup-shaped recess, and said locking lugs are formed on and spaced apart about the periphery of the exterior of the breechblock, a first longitudinal recess formed on the exterior surface of the breechblock in a first space between the locking lugs, for receiving a cartridge extracting means carried by the breechblock, and a second longitudinal recess formed in the exterior surface of the breechblock in a second space between the lugs which is opposed from the first longitudinal recess, the depth of the second longitudinal recess into the breechblock being sufficient so that the second longitudinal recess intersects the said cup-shaped recess at the forward end of the breechblock to provide a passage for a cartridge ejector carried by the breechcase, said extracting means comprising an extractor member held in place to engage a cartridge by a heel part which pivotably engages a front part of the breechblock, and including a leafspring mounted in said first recess, the rearward end of this leaf-spring being held against the breechblock and the forward end of the leaf-spring being biased outwardly against said heel part, thus maintaining the extractor member in place both radially and longitudinally relative to the breechblock.

2. A breech mechanism as claimed in claim 1 wherein the angular spacing measured between the adjacent lugs defining said first space is twice the average angular spacings measured between the remaining adjacent lugs.

3. A breech mechanism as claimed in claim 2 wherein said first space is (2 (360))/(2n+l) and at least one of the remaining spaces is 360/2n+l, wherein 2n equals the number of lugs extending about the periphery of the breechblock.

4. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking of said forward or arward ositions of the casin re ative to the breec lock, arid means for lockin g t e breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place when the breechblock has substantially reached its front closing portion at which it closes off the rear end of the barrel, the said means at the forward end of the breechblock comprises a cup-shaped recess, said locking lugs being formed on and spaced apart about the periphery of the exterior of the breechblock, a first longitudinal recess formed on the exterior surface of the breechblock in a first space between the locking lugs, a cartridge extracting member carried by the breechblock in said recess, and a spring located in a groove formed onto the exterior surface of the breechblock and having one end fixed to the breechblock withinthe fluid tight chamber and biased radially outwardly of the breechblock axis for urging the cartridge extracting member to its cartridge holding position, said recess guiding said extracting member to prevent lateral movement thereof relative to the breechblock, and a second longitudinal recess formed in the exterior surface of the breechblock in a second space between the lugs which is opposed from the first longitudinal recess, the depth of the second longitudinal recess into the breechblock being sufficient so that the second longitudinal recess intersects the said cup-shaped recess at the forward end of the breechblock to provide a passage for a cartridge ejector carried by the breechcase.

5. A breech mechanism as claimed in claim 4 said breechblock including a raised annular enlargement formed thereon in the fluid tight chamber, said enlargement engaging forward and rearward walls of the fluid tight chamber to limit the forward and rearward movement, respectively, of the breechblock, relative to the casing.

6. A breech mechanism as claimed in claim 5, said means for locking including a rod attached to the easing and engaging helical surfaces in the said enlargement of the breechblock.

7. A breech mechanism as claimed in claim 5, including a nut fixing the said one end of the spring in the fluid-tight chamber, said nut formed in the said enlargement. 

1. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase about the breechblock for longitudinal sliding movement, and means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place when the breechblock has substantially reached its front closing position at which it closes off the rear end of the barrel, the improvement wherein: the said means at the forward end of the breechblock comprises a cup-shaped recess, and said locking lugs are formed on and spaced apart about the periphery of the exterior of the breechblock, a first longitudinal recess formed on the exterior surface of the breechblock in a first space between the locking lugs, for receiving a cartridge extracting means carried by the breechblock, and a second longitudinal recess formed in the exterior surface of the breechblock in a second space between the lugs which is opposed from the first longitudinal recess, the depth of the second longitudinal recess into the breechblock being sufficient so that the second longitudinal recess intersects the said cup-shaped recess at the forward end of the breechblock to provide a passage for a cartridge ejector carried by the breechcase, said extracting means comprising an extractor member held in place to engage a cartridge by a heel part which pivotably engages a front part of the breechblock, and including a leafspring mounted in said first recess, the rearward end of this leaf-spring being held against the breechblock and the forward end of the leaf-spring being biased outwardly against said heel part, thus maintaining the extractor member in place both radially and longitudinally relative to the breechblock.
 2. A breech mechanism as claimed in claim 1 wherein the angular spacing measured between the adjacent lugs defining said first space is twice the average angular spacings measured between the remaining adjacent lugs.
 3. A breech mechanism as claimed in claim 2 wherein said first space is (2 (360*))/(2n+1) and at least one of the remaining spaces is 360*/2n+1, wherein ''''2n'''' equals the number of lugs extending about the periphery of the breechblock.
 4. In a breech mechanism of the type for use with an automatic or semi-automatic gun comprising a breechblock mounted in a breechcase having a barrel cooperating therewith, said breechblock adapted to be locked by cooperation between the barrel and locking lugs formed on the breechblock, means at the forward end of the breechblock for receiving the rear end of cartridges to be fired, a casing non-rotatably mounted in the breechcase around the breechblock for longitudinal sliding movement in the breechcase and between a forward position and a rearward position, relative to the breechblock, means for forming a generally annular and generally fluid tight chamber between the outside of the breechblock and the inside of the casing in either of said forward or rearward positions of the casing relative to the breechblock, and means for locking the breechblock by transforming into rotary movement of the breechblock at least a part of the longitudinal movement of the casing, relative to the breechblock, which relative movement takes place when the breechblock has substantially reacheD its front closing portion at which it closes off the rear end of the barrel, the said means at the forward end of the breechblock comprises a cup-shaped recess, said locking lugs being formed on and spaced apart about the periphery of the exterior of the breechblock, a first longitudinal recess formed on the exterior surface of the breechblock in a first space between the locking lugs, a cartridge extracting member carried by the breechblock in said recess, and a spring located in a groove formed onto the exterior surface of the breechblock and having one end fixed to the breechblock within the fluid tight chamber and biased radially outwardly of the breechblock axis for urging the cartridge extracting member to its cartridge holding position, said recess guiding said extracting member to prevent lateral movement thereof relative to the breechblock, and a second longitudinal recess formed in the exterior surface of the breechblock in a second space between the lugs which is opposed from the first longitudinal recess, the depth of the second longitudinal recess into the breechblock being sufficient so that the second longitudinal recess intersects the said cup-shaped recess at the forward end of the breechblock to provide a passage for a cartridge ejector carried by the breechcase.
 5. A breech mechanism as claimed in claim 4 said breechblock including a raised annular enlargement formed thereon in the fluid tight chamber, said enlargement engaging forward and rearward walls of the fluid tight chamber to limit the forward and rearward movement, respectively, of the breechblock, relative to the casing.
 6. A breech mechanism as claimed in claim 5, said means for locking including a rod attached to the casing and engaging helical surfaces in the said enlargement of the breechblock.
 7. A breech mechanism as claimed in claim 5, including a nut fixing the said one end of the spring in the fluid-tight chamber, said nut formed in the said enlargement. 